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TITLE: TUNING STEPS CHANGE FOR ALL MODE ICOM IC-275/475/575/1275

The IC-275/475 FM-Step select matrix use these diodes on the front unit:
(type 1SS53)  D41, D42, D43, D44, (D45), D46

Note: diode D45 is not present but solder holes exist for it on the board
      just between D44 e D46

installed diodes are marked with X :

                (*)     (*)
D41 D42 D43 D44 D45 D46 D48    Steps     DB4 DB5 DB6 DB7
 .   .   .   .   .   .   .    10.0  Hz
 .   .   .   X   .   .   .   100.0  Hz    1   0   0   0
 .   X   .   .   .   .   .     1.0 KHz    0   0   1   0
             X   .   X   .     5.0 KHz    1   0   1   0
 .   .   .   .   X   .   .    10.0 KHz    0   1   0   0
 .   .   .  (*)  X   X   .    12.5 KHz   (*)  1   1   0
 .   .   .   .   .   .   X    25.0 KHz    0   0   0   1
 X   .   X   .   .   .   .     1.0 MHz    0   1   0   1


(*) To set a step of 12.5 KHz in FM mode (TS button off) it is not
    necessary disconnect the diode D44, just insert the diode D45
    (IN4148 or similar) near D44 and "voil… les jeux sont faits".
    Unscrew the two lateral screws and unlock the front panel.
    Remove also all the connectors of the front board and after that
    unscrew ALL the screws of the metallic shield covering the front board.
    It seems too much complicated the insertion of the diodes from the
    component side of the front board, so it is better to solder D45 on
    the solder side.

  '73 de IK1OOM


   IK1OOM @ I1NHK Roberto ORLANDINI - Rivoli (TO) - ITALY
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